In modern manufacturing, material fatigue failure is one of the main reasons for the failure of engineering structures and mechanical components. In order to improve the fatigue life of parts, extend their service life, and enhance reliability, shot peening processing (Shot Peening) as an effective surface strengthening process is widely used in key components of industries such as aviation, automotive, rail, and shipping.



Shot peening processing is a cold working process that uses high-speed jetting of small metal shots to impact the surface of the workpiece. Its main function is to introduce residual compressive stress into the material surface through surface plastic deformation, thereby significantly improving the material's fatigue resistance. This process not only strengthens the surface but also seals tiny cracks and defects, reduces stress concentration, and delays the initiation and propagation of fatigue cracks.

　　Firstly, shot peening processing increases the fatigue life by forming a compressive stress layer on the surface of the workpiece. Under the action of alternating loads, the surface of the material is often the easiest location for fatigue cracks to initiate. The compressive stress introduced by shot peening can offset part of the external tensile stress, thereby reducing the probability of crack formation. Experiments show that components treated with appropriate shot peening can have their fatigue strength improved by 20% to 100%, with a significant increase in fatigue life.



Secondly, shot peening can improve the microstructure of the material surface. During the shot peening process, the high-speed impact of the shot particles refines the surface grains and induces an increase in dislocation density, thereby enhancing the hardness and strength of the material. This 'work hardening' effect makes the surface more difficult to undergo plastic deformation or crack propagation, further improving the fatigue performance.

　　Moreover, shot peening can also repair surface defects. During casting, welding, or cutting processing, the surface of the material may have defects such as microcracks, scale, or machining marks. The shot peening process can effectively remove these defect layers, making the surface more uniform and dense, and reducing the formation of fatigue crack sources.



In practical applications, parameters of the shot peening process such as shot size, jet speed, coverage, and jet angle will all affect the final strengthening effect. Therefore, the rational selection and control of these parameters are crucial to ensuring the effectiveness of shot peening. For example, in high-stress components such as aeroengine blades, gears, and springs, strict shot peening specifications are usually adopted to ensure the optimal improvement of fatigue life.

　　In summary, shot peening processing effectively improves the fatigue life of materials through various mechanisms such as introducing residual compressive stress, refining grain structure, and eliminating surface defects. As an economical, efficient, and environmentally friendly surface strengthening technology, shot peening plays an irreplaceable role in enhancing the reliability of engineering components, and its importance in modern industry will become increasingly prominent with the continuous improvement of product performance requirements.